1. Field of the Invention
This invention relates to a method for determining the magnitude of the fluid drift rate in a formation penetrated by a well.
2. Description of the Prior Art
The determination of fluid drift rate in a reservoir is of major importance in obtaining a satisfactory understanding of the conditions within any given reservoir. The fluid drift rate represents the velocity of reservoir fluid particles as they pass through the zone of investigation, their movement being produced by forces outside the zone of investigation. Such information is critical to the prediction of such behavior as the motion of the injected fluid fronts through the reservoir and for the design of the most efficient pattern of injection and production wells for the exploitation of the fluids contained within the reservoir.
Heretofore the most common method for determining a fluid drift rate in a reservoir has been to inject a tracercontaining fluid into one injection well and then to monitor the surrounding production wells for the appearance of the tracer-containing fluid and calculating therefrom the fluid drift rate from the distance between said injection and production wells and the time necessary for the tracer to travel there between. Two disadvantages to this method are readily apparent. First, it is necessary to monitor several production wells in order to have a high probability that the tracer will break through into at least one of the production wells. Another disadvantage is that the injection well will commonly be separated from the production wells by distance of at least several hundred meters. Under such conditions the waiting time required between the injection of the tracer and its production at one of the monitor wells can easily take months.
There remains at this time a need for a method of determining the fluid drift rate in a reservoir which uses only one well and that can be practiced inexpensively within short time periods giving accurate results.